1. Field of the Invention
One or more aspects of the invention generally relate to graphics processing, and more particularly to connecting graphics processors in a multi-processor graphics processing system.
2. Description of the Related Art
Conventional multi-processor graphics processing systems, such as 3dfx's VooDoo2™ graphics adapter product configured for scan line interleave (SLI) or Metabyte/Wicked 3D's parallel graphics configuration (PGC), increase graphics processing performance by using two or more graphics adapters. Motherboard 100, shown in FIG. 1, is an example of a conventional multi-processor graphics processing system. Motherboard 100 includes a host processor 120, a main memory 110, and a chipset 130 which is provides an industry standard interface, specifically peripheral component interface (PCI), to each graphics adapter 140. A first graphics adapter 140 and a second graphics adapter 140 are each coupled to motherboard 100 via connectors and instructions and data are broadcast from host processor 120 via PCI bus 142. The first graphics adapter 140 renders a first half, e.g. odd scan lines or the top half, of an image for display on a display 170 and the second graphics adapter 140 renders a second half of the image.
The first graphics adapter 140 converts the digital data for the first half of the image to the analog domain using a first digital to analog converter (DAC) within an analog combining unit 150 and outputs analog video signals to an analog combining unit 150 within the second graphics adapter 140 using a proprietary cable 145 configured to transfer analog signals. The second graphics adapter 140 converts the digital data for the second half of the image to the analog domain using a second DAC within another analog combining unit 150. The analog combining unit 150 within the second graphics adapter 140 combines the analog video signals received from the first graphics adapter 140 with analog video signals generated based on the second half of the image to produce an analog video output for the entire image. The analog video output for the entire image is output to display 170. Differences in video timing and DAC calibration between the first graphics adapter 140 and the second graphics adapter 140 introduces visual artifacts, such as tearing and color variations, during display of the entire image.
Accordingly, it is desirable to facilitate installation of two or more graphics adapters to produce an image free of artifacts resulting from video timing and DAC calibration differences.